The main objective of this application is to determine whether the xenoestrogenic substances bisphenol A (BPA) and butyl benzyl phthalate (BBP) play a role in the initiation of human breast cancer, and if so, whether this effect is mediated by epigenetic mechanisms. The proposed study is based on the growing concern that estrogenic environmental compounds that act as endocrine disrupting chemicals might have potential adverse effects on hormone-sensitive organs such as the breast. This concern is further fueled by evidence indicating that natural estrogens, namely 17 [unreadable]-estradiol (E2), are important factors in the initiation and progression of breast cancer. Therefore, the concern that BPA and BBP, which have estrogenic properties and are widely distributed in the environment, might also be carcinogenic for the human breast is well justified. For accomplishing these goals we will utilize our in vitro in vivo model in which we have demonstrated the carcinogenicity of E2 in the human breast epithelial cells MCF-10F. The utilization of this powerful and unique model will provide us a tool for exploring whether BPA and BBP have relevance in the initiation of breast cancer. Furthermore, we have found that the expression of E2-induced transformation phenotypes is associated with hyper or hypomethylation of genes controlling branching and ductulogenesis. These are the basis for our rationale to postulate that the xenoestrogens BPA and BBP can induce neoplastic transformation by behaving as epigenetic modulators inducing silencing of critical genes by hypermethylation and/or histone modification that lead to the initiation and progression of breast cancer. For this purpose, we propose the following specific aim: To determine whether the xenoestrogens BPA and BBP induce neoplastic transformation in human breast epithelial cells and whether the expression of transformation phenotypes is associated with epigenetic changes in genes controlling branching and ductulogenesis, and if this is the case, to determine if modifying their methylation status reverts the neoplastic process. To accomplish this aim we will use MCF-10F cells and primary cultures of human breast epithelial cells obtained from reduction mammoplasty. The cells will be treated with BPA and BBP using a protocol similar to that used for the treatment of these cells with E2, which will serve as a control. Methylation studies will be performed using Restriction Landmark Genomic Scanning (RLGS) and the identified genes will be further studied using methylation specific PCR (MSP) followed by confirmation of their expression and functional role. Altogether, these studies will provide first hand evidence on whether xenoestrogenic substances are able to induce neoplastic transformation in HBEC and that epigenetic mechanisms are involved in this process. Furthermore the manipulation of the methylated status and silencing of those epigenetically modified genes will provide not only an understanding of how these environmental contaminants are involved in breast cancer initiation but also will give us tools for developing preventive strategies to counteract their effect in the general population. RELEVANCE TO PUBLIC HEALTH: These studies will provide first hand evidence on whether xenoestrogenic substances like BPA and BBP are able to induce neoplastic transformation in HBEC and that epigenetic mechanisms are involved in this process. Furthermore the manipulation of the methylated status and silencing of those epigenetically modified genes will provide not only an understanding how these widely environmental contaminants are involved in breast cancer initiation but also for developing preventive strategies to counteract their effect in the general population. [unreadable] [unreadable] [unreadable]